1. Field of the Invention
This invention relates to a solar energy collector and, more particularly, to a lightweight, low cost solar energy collector.
2. Prior Art
There has long existed the need for a high performance, low cost solar collector. Solar collectors have generally been made using high cost materials including copper, stainless steel, aluminum, and tempered glass. The use of such materials has contributed to additional costs during processing as necessitated by the required configuration. Further costs are added on due to the weight incurred by such solar collectors in transportation, labor, and equipment used for installation, and in some cases structural reinforcements needed for existing installation sites.
Such metal prior art solar collectors consist of an absorber member, a means for transferring the absorbed energy to a fluid, usually water, a transparent cover or glazing, and an insulated frame which acts as a support for the absorber and glazing. The principle application of these devices is to heat water for domestic, industrial or commercial needs.
In recent years many solar collectors have been disclosed in patent literature which teach using one or more synthetic polymer materials. These patents suggest a plurality of solar collectors for an apparent variety of uses. However, because of the type of polymers used or because of the design, or both, such collectors are limited to low temperature application. Thus, in order to achieve higher temperature, many still continue to use collectors made from metal.
Representative examples of solar collectors which are made in whole or in part of polymeric materials are shown in U.S. Pat. Nos. 4,239,035; 4,221,210; 4,096,861; 3,934,323; 4,114,596; and 3,991,742. Referring specifically to the U.S. Pat. No. 4,221,210, there is disclosed a solar collector made from a synthetic material in which a liquid containing carbon particles is circulated. The reflective surface consists of a layer of aluminum or other metallic material placed outside the rear panel. Such a design effects a low to moderate absorption temperature. Absorbtivity is increased with the black fluid which simultaneously removes the heat. This patent also teaches that the solar panel can be made from polycarbonates, acrylics or glass.
Polycarbonates usually have a UL rating for continuous operating temperatures of less than 240.degree. F., which is the upper limit for practical use. Commercialization of such a collector would thus require that absorber stagnation temperatures not exceed 239.degree. F., which limits the collector design to that of low temperature and low efficiency. Furthermore, polycarbonates are subject to hydrolysis in hot water which limits their usefulness, and certainly, their life expectancies. Acrylics have a maximum UL rating for continuous operating temperature of only 200.degree. F. Glass is impractical for solar collectors because of breakage. Moreover, a multi-channel panel made from glass presents immense processing problems. Other similar teachings are disclosed in U.S. Pat. Nos. 4,239,035 and 4,096,861.
Other problems are associated with such solar collector systems. For example, particles, pigments, and dyes added to the fluid tend to plate out on the panel surface resulting in a diminishing level of light passing through to the fluid. Fluid additives can also precipitate in the system causing clogging and flow restrictions. The fluid can also become non-uniform, thereby adversely affecting performance.
U.S. Pat. No. 3,934,323 discloses a non-glazed multichannel solar panel made from polyethylene-fitted hollow headers wherein a fluid is pumped through exchanging heat with the environment. Such a configuration limits the system to low temperature applications such as providing heat for swimming pools. U.S. Pat. No. 3,991,742 is similar and is also limited to low temperature applications. U.S. Pat. No. 4,114,596 discloses a unitary solar collector made from polycarbonate or acrylics. As pointed out previously, these materials are temperature limited.
Thus, there still exists a need for a low cost solar collector capable of high thermal performance which can be mass produced using existing, readily available, lightweight materials.
The present invention has solved these and other problems by a unique design and the use of light weight plastic components. The present invention contemplates a configuration which allows forgiveness for lack of certain properties in the plastics used thereby permitting the use of various thermoplastics in the solar collector to fulfill a specific function. The overall result is a low cost, high thermal performing, light weight unit which lends itself to mass production.
The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objectives and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawing in which a presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only and is not intended as a definition of the limits of the invention.